fuel economy

sungear

Want to get some advice regarding decreasing fuel efficiency.

Car is getting less miles per full tank as of recently, just want to know if clutch going would be indicated by a reduced revs per mph, thought it would have been the other way around.

Also how many thousand miles would be considered good between clutch change??

fletch

The cold weather effects your mpg, mine has dropped ~5mpg in the last couple of weeks.

sungear

appreciate the reply but thought temp difference would be taken into account by electronic engine management?
I prob haven't given the full details tho in an effort to keep it brief, used to get 3k revs at 60mph in 5th gear but that has dropped a bit to about 2800, plus where I used to be at nearly 4k revs at 70mph its barely above 3k, I'd thought a slipping clutch would mean higher revs, I've gone a long way without changing the clutch anyway but interested to get an opinion from anyone thats come across a similar situation, due a service so haven't even looked at the air filter, too bloody cold.

peasant

I used to be at nearly 4k revs at 70mph its barely above 3k

So your car has just become faster?

Have you fitted larger tyres, or what?

Anan1

Larger tyres would make the car faster, but the speedo would still read the same.;)

congo_90

now this may sound a bit sarcastic but has your seat moved at all so to move your position and hence your perspective of the instrument panel??

If not perhaps your car is somehow running more efficient when warmed up due to the denser air entering your engine thus reducing how much fuel to air is required and returning better power?

sungear

Seat is definitely in the same position, no parallex error,
fuel economy down, whats good mileage between clutch change?

Alanstrainor

Doesn't sound like a clutch going tbh, that would see the revs creeping higher when accelerating, and a noticeable lack of acceleration. The symptoms you mention seem strange, lower revs and yet lower fuel efficiency?

Anan1

sungear wrote: »

Seat is definitely in the same position, no parallex error,
fuel economy down, whats good mileage between clutch change?

Depends entirely on your driving. In a normal car that's not being abused or doing too much stop/start, 200,000kms should be easily achievable.

sungear

thats what had me, obviously something else with the fuel efficency, I'm suprised I got this much mileage out of it thats why wanted to get an idea of the potential life of the clutch, just dont get why my revs are down, maybe it is the temp drop recently.

sungear

Cheers for the info, 200,000kms ,well not there yet , dont think I abuse it but, ive had others on the insurance briefly, better get the air filter out and have a look.
I've read fords are renowned for early timing belt failure any opinions?

Henry Ford III

How can the engine revs drop at a given speed?

sungear

thats what I was querying, almost same as before at 60mph in 5th gear but not the same increase in revs that i used to have up to 70mph? I assumed something was wrong in the clutch but guessed that a slipping clutch would increase revs??

Anan1

TBH, the figures aren't adding up. The OP was getting 60mph for 3,000rpm but only 70mph for 4k rpm, whereas it should be 80mph. This could be explained by a slipping clutch.

The current figures though, 2800rpm at 60mph and just over 3k rpm at 70mph, sound fine.

The only things I can think of are:

The clutch was slipping but isn't now - might some contaminant have leaked onto it and subsequently burnt off?

or

The speedo or rev counter (or both) is/are on the way out.

This is only me thinking aloud though, i'm no mechanic.:)

snowman707

you havn't reconfigured your speedo from kph to mph by any chance


stupid suggestion i know but i have heard of it happening

Biro

Anan1 wrote: »

TBH, the figures aren't adding up. The OP was getting 60mph for 3,000rpm but only 70mph for 4k rpm, whereas it should be 80mph. This could be explained by a slipping clutch.

The current figures though, 2800rpm at 60mph and just over 3k rpm at 70mph, sound fine.

The only things I can think of are:

The clutch was slipping but isn't now - might some contaminant have leaked onto it and subsequently burnt off?

or

The speedo or rev counter (or both) is/are on the way out.

This is only me thinking aloud though, i'm no mechanic.:)

Sounds like a mis-reading more than anything else. Does it sound any different at 70mph?

sungear

Not really any different sounding, was thinking today the tacho maybe out? see someone has mentioned that, due a service so gonna do that and see if it makes a difference.
New on boards so thanks for all the pointers

Biro

sungear wrote: »

Not really any different sounding, was thinking today the tacho maybe out? see someone has mentioned that, due a service so gonna do that and see if it makes a difference.
New on boards so thanks for all the pointers

If it doesn't sound any different then maybe the reading from the dials is arseways. I've seen it happen before.

ianobrien

Don't forget that in Winter, you'll have the heater on, lights on, rear window on etc and they'll all increase the fuel consumption due to increased load on the engine.

To see the what I'm on about, on a warm engine, turn on the heater, rear window demister and lights on, and watch the load drop the engine speed.

Biro

ianobrien wrote: »

Don't forget that in Winter, you'll have the heater on, lights on, rear window on etc and they'll all increase the fuel consumption due to increased load on the engine.

To see the what I'm on about, on a warm engine, turn on the heater, rear window demister and lights on, and watch the load drop the engine speed.

The load will only drop the engine speed when in neutral, it can't possibly drop the engine speed when in gear without dropping car speed.

mickdw

Biro wrote: »

The load will only drop the engine speed when in neutral, it can't possibly drop the engine speed when in gear without dropping car speed.

but the load will increase fuel consumption which is the point he was making.

Biro

mickdw wrote: »

but the load will increase fuel consumption which is the point he was making.

That's true, but based on the rest of the thread, which has steered towards the RPM versus the MPH discussion it was a bit out of place.

craichoe

Tachometer is giving incorrect readings.

samih

<sarcasm>It's still possible that somebody has changed OP car's final drive without telling him. The new taller gearing is too much for the 1.1 engine and his fuel consumpition suffers.</sarcasm>

ianobrien

Biro wrote: »

That's true, but based on the rest of the thread, which has steered towards the RPM versus the MPH discussion it was a bit out of place.

The OP said that his fuel consumption was increasing.

The discussion then went on about gearing, rev counters etc which don't answer the question. If the clutch was slipping, it would slip initially under load (accelerating) and not while cruising. If the clutch was slipping while cruising, then the OP would notice the pronounced clutch slip while accelerating, and probably the smell.

To check the rev counter and clutch slipping, open the window and floor it. As the engine note changes, the revs should as well, along with the speed of the car. If the revs increase with no increase in speed - Clutch gone.

The typical reasons for increased fuel consumption (increased electrical load, increased load in car, tyre pressures, change of tyres etc.) should be looked at first before rushing off like that.

I'm assuming that there is no change in driving style, average, max and cruising speeds, change in times stopped in traffic, change in route or road surface as well........